The present invention relates to a fish growth hormone derived from an eel and a process for producing the eel growth hormone. The present invention also pertains to a process for stimulating growth of a fish using the eel growth hormone. A growth hormone is secreted from the anterior lobe of hypophysis of vertebrates, and is a polypeptide which has a function of promoting increase in weight by adjusting a rate of incipient growth of the bone. Therefore, the present invention is expected to be of great utility in an industrial field of fish cultivation.
Mammalian growth hormones are produced in the pituitary gland. The activity and structure of the mammalian growth hormones are known. For example, human growth hormones have been reported in J. Am. Chem. Soc., 80, 4429 (1958) by U. J. Lewis, et al.; Biochem. J., 100, 754 (1966) by A. S. Hartree; and Arch. Biochem. Biophys. (Suppl.), 1, 327 (1962) by C. H. Li, et al.
As for fish growth hormones, there have been some. reports on the isolation thereof, examples of which are given below.
Isolation from Tilapias PA0 Isolation from Sturgeons PA0 Isolation from Carp PA0 Isolation from Chum salmon
S. W. Farmer, et al., Gen. Comp. Endocrin., 30, 91 (1976) PA1 S. W. Farmer, et al., Endocrinology, 108, 377 (1981) PA1 A. F. Cook, et al., Gen. Comp. Endocrin., 50, 335 (1983) PA1 Japanese Published Unexamined Patent application No. 214798/85
On the other hand, as for mammalian growth hormone genes, rat growth hormone gene [P. H. Seeburg, et al., Nature 270, 486 (1977)], bovine and swine growth hormone genes [P. H. Seeburg, et al., DNA, 2, 37 (1983)]and human growth hormone gene [J. A. Martial, et al., Science, 205, 602 (1979)]are already known. Further, as for fish growth hormone genes, chum salmon growth hormone gene was already known by the hand of the present inventors (Japanese Published Unexamined Patent Application No. 15699/86).
However, there is no report about isolation of a growth hormone from eels, eel growth hormone genes and a process for producing an eel growth hormone polypeptide by recombinant DNA techniques using the genes.
Fish growth hormones have the effect of stimulating the growth of fish, and thus are useful as a component of baits for fish cultivation. Examples in recovery of fish growth hormone from the fish pituitary gland are known as described above, and nevertheless, it has been desired that a fish growth hormone having more excellent stimulating effect is developed. Further, the amount of the growth hormone provided by the recovery from the fish pituitary gland is limited. Therefore, it has been desired that a process for providing a large amount of fish growth hormones in a low cost is developed.